Magnetic coil support having magnetic and non-magnetic flanges



1965 HIROMI MATSUlI/IOTO 3,284,748

MAGNETIC COIL SUPPORT HAVING MAGNETIC AND NON-MAGNETIC FLANGES FiledJune 25, 1964 FIG. I FIG. 2 FIG. 3

PRIOR ART INVENTOR.

M. MMID BY MnuLu. f, Mhm

United States Patent 3,284,748 MAGNETIC COIL SUPPORT HAVING MAGNETIC ANDNON-MAGNETIC FLANGES Hiromi Matsumoto, Tokyo-to, Japan, assignor to TakeKabushiki Kaisha, Tokyo-to, Japan, a joint-stock company of Japan FiledJune 23, 1964, Ser. No. 377,224 Claims priority, application Japan, June24, 1963, 38/33,?)20, 38/46,895 6 Claims. (Cl. 336-233) This inventionrelates to inductance devices such as small-size intermediate frequencytransformers to be used for transistors and various other inductancedevices.

It is a principal object of the invention to provide inductance devicesin which the range of inductance variation is wide, fine adjustment ofthe inductance value can be easily accomplished, and the construction isstable, and which can be produced by mass production technique.

Another object of the invention is to provide a magnetic core for a coilhaving a wide range of induction variation.

Further objects and advantages of the present invention will becomeapparent, and this invention will be better understood from thefollowing description, reference being made to the accompanyingdrawings, in which the like parts are designated by like referencecharacters, and in which:

FIG. 1 is a side view of an inductance device utilizing a conventionaldrum core;

FIG. 2 is a diagrammatic representation of the principle of a variableinductance device;

FIG. 3 is a sectional view of one embodiment of this invention;

FIG. 4 is a sectional view of a modification of this invention;

FIG. 5 is a perspective view of the core shown in FIG. 4;

FIG. 6 is a sectional view of another modification of this invention;and 1 FIGS. 7 through 9, inclusive, are partly sectional viewsrespectively showing further modifications of the core according to theinvention.

Referring now to the accompanying drawings, there is shown in FIG. 1 aconventional drum core utilized in small size intermediate frequencytransformers comprising a yoke or main body 3 and flanges 2 on theopposite ends thereof between which a coil 4 is wound around the yoke 3.These flanges and the yoke are formed or molded as a unitary structurefrom a suitable magnetic material. With this type of core, the range ofinductance variation is increased with decrease in the diameter d orthickness t of the flange 2 to which an adjusting core of magneticmaterial, not shown, is to be made to approach, because when thediameter d or thickness t of the flange 2 is increased, the reluctanceof the magnetic path through the magnetic path shown by dotted lines Ais decreased and becomes less affected by external magnetic material.

As a result, in an extreme case, an ideal characteristic could beprovided if the flange 2 on the side of the adjusting core wereeliminated so as to wind a coil 4 on a T- shaped magnetic corecomprising a yoke 3 and a flange 1 only, as shown in FIG. 2. In thiscase, the adjusting core 5 acts as a portion of the magnetic path, thusgreatly increasing the sensitivity of the inductance device to thedisplacement of the adjusting core. With this construction, however, itis very diflicult, or impossible, to wind the coil 4 on the yoke 3.

In prior small intermediate frequency transformers, it has been thepractice to securely fix the drum core and the coil mounted thereon to abase by means of an adhesive or any of various other mounting means, butsuch means are not advantageous from the standpoint of construction,mass production and strength of mounting.

'stituted to mount the adjusting core.

"ice

In order to overcome the various difficulties mentioned above, inaccordance with this invention, there is provided a T-shaped magneticcore 6 comprising a yoke or main body-3 and a flange 1 on only one ofits ends. The core is provided with a through opening 7 extendingaxially through the yoke and its flange. When the flange 1 is cast in abase 8 of a nonmagnetic material such as a synthetic resin, a portion ofthe nonmagnetic material is led through this opening 7 to form a flange9 of nonmagnetic material on the opposite side of the core.

It is to be understood herein that the term nonmagnetic material used toform said base 8 and the flange 9 is intended not only to mean theordinary nonmagnetic mate-' rials but also to include weak magneticmaterials having relatively lower permeability than the magneticmaterial constituting the flange 1 and the yoke 3 as well as diamagneticmaterials.

In the embodiment shown in FIG. 3, since the upper end of the yoke 3 isflat and is covered by the flange 9, the maximum value of ,u. isrelatively small due to the presence of nonmagnetic material between theadjusting core 5 and the core 6. To overcome this difliculty, radialgrooves 10 are cut in the end surface of the yoke 3, as shown in FIG. 5,to mold radial flanges 9 in the grooves 10, thereby to leave a portionof the end surface exposed. This is best shown in FIG. 4. In this case,the maximum value of ,u. is greatly increased because the magnetic core6 and the adjusting core 5 can directly contact each other.

In another embodiment shown in FIG. 6, an intermediate flange 9 is alsomolded by forming one or more radial openings 11 through the wall of thecore so as to guide a portion of the molding material contained in thethrough opening 7 through these radial openings.

As shown in FIG. 3, suitable terminal pins 12 are cast in the base 8 orinserted therein subsequent to its molding operation and screw threads13 are cut to receive the adjusting core 5. It should be understood,however, that any one of a number of well known means may be sub- Forexample, an annular vertical rib may be formed to be spaced apart fromthe magnetic core, and screw threads may be cut on the inner surface ofthe annular rib to receive cooperating threads provided on the outersurface of the adjusting core 5.

Thus, according to this invention, as the upper flange 9 of the T-shapedmagnetic core 6 is formed by the molding material which constitutes thebase 8, the electromagnetic characteristic of the novel core isequivalent to a magnetic core wherein a flange on one side has beenremoved, thus widening the range of inductance variation, but the novelcore is mechanically equivalent to the conventional configuration sothat the winding operation for the coil 4 can be carried out veryeasily.

Moreover, as the T-shapedmagnetic core 6 is rigidly clamped between thebase 8 and the flange 9, it is not required to cement or to use specialmounting means. Further, as the base and the flange are made by castingoperation, the novel core can be manufactured by mass productiontechnique at low cost.

According to another embodiment of the core of this invention, as shownin FIGS. 7 to 9, inclusive, the yoke 3 and only one flange 1 thereof areformed or molded from a magnetic material, the other flange 9 and atubular member 14 to be fitted on the yoke 3 are molded integrally froma nonmagnetic material, and the winding 4 is wound on the tubular member14.

FIG. 7 shows one form of the core of this invention wherein both ends ofthe tubular member 14 are opened to expose the outer end of the yoke 3.FIG. 8 shows a modification wherein one end of the tubular member 14 isclosed by the flange 9 In a still further modification 3 shown in FIG.9, the lower end of the tubular membe 14 provided with anupper flange 9,is provided with an additional flange 9 which is placed in contactagainst the upper surface of the magnetic flange 1. Although a suitableadhesive and the like may be applied between the tubular member 14 andthe yoke 3 and between flanges 1 and 9 even where the tubular member 14is merely fit on the yoke 3, as the coil 4 is wound on the tubularmember 14, the member 14 will be urged inwardly to be rigidly fixed uponthe yoke. Thus, the tubular member 14 is prevented from disengaging,thereby to firmly secure the flange 9.

As shown in FIG. 7, when the top surface of the yoke 3 is exposed byproviding a through opening in the tubular member 14, the adjustablecore 5 can contact this exposed top surface to advantageously increasethe maximum value of 41 While specific embodiments have been disclosedto illustrate the invention, it will be understood that manymodifications and variations may be made within the true spirit andscope of the invention as defined in the appended claims.

What is claimed is:

1. A magnetic core for a coil consisting of a yoke of magnetic material,a first flange made of magnetic material fixed to one end of said yoke,a tubular member of nonmagnetic material, said tubular member beingadapted tosupport a coil, and a second flange of nonmagnetic materialand connected to the other end of said tubular member remote from saidfirst flange.

2. The magnetic core according to claim 1 wherein said first flange andsaid yoke are molded integrally from a magnetic material, and saidtubular member and said second flange are molded integrally from anonmagnetic material.

3. The magnetic core according to claim 1 wherein said second flange andsaid tubular member are provided with a through opening to expose thefree end of said yoke.

4. The magnetic core according to claim 1 wherein said second flange issolid to seal the free end of said yoke.

5. An inductance device comprising a magnetic core including acylindrical magnetic yoke, a magnetic flange combined with said yoke,and an opposite flange of said yoke; an opening extending axiallythrough said yoke; a nonmagnetic base; said magnetic flange being castin said base; the opposite flange being molded as an extension of saidnonmagnetic base; said extension being unified with said base bynonmagnetic material filling said opening; anda coil Wound about saidyoke.

6. The inductance device as defined in claim 5, wherein the yoke endopposite said magnetic flange is provided with one or more radialgrooves, and part of the nonmagnetic flange is cast in said radialgrooves.

References Cited by the Examiner UNITED STATES PATENTS 2,223,056 11/1940Berthold 336212 X 2,433,207 12/ 1947 Eilenberger 336-198 X 2,905,9139/1959 Leigh 33683 3,017,590 1/1962 Chass 336-436 FOREIGN PATENTS907,803 3/ 1954 Germany.

LEWIS H. MYERS, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

D. J. BADER, Assistant Examiner.

1. A MAGNETIC CORE FOR A COIL CONSISTING OF A YOKE OF MAGNETIC MATERIAL,A FIRST FLANGE MADE OF MAGNETIC MATERIAL FIXED TO ONE END OF SAID YOKE,A TUBULAR MEMBER OF NONMAGNETIC MATERIAL, SAID TUBULAR MEMBER BEINGADAPTED TO SUPPORT A COIL, AND A SECOND FLANGE OF NONMAGNETIC MATERIALAND CONNECTED TO THE OTHER END OF SAID TUBULAR MEMBER REMOTE FROM SAIDFIRST FLANGE.